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Analysis of Ground-based FTIR Measurements at Toronto

Fourier transform infrared (FTIR) spectrometers are powerful instruments capable of making atmospheric profile measurements of various trace gases. In this study, measurements made from 2002 to 2017 by a FTIR spectrometer situated at the University of Toronto Atmospheric Observatory (TAO) was analyzed for biomass burning enhancement events as well as general trends in the data. Emission factors (EF) and emission ratios (ER) were calculated for biomass burning enhancement episodes in 2012, 2015 and 2017. HYSPLIT trajectory model was used for travel time estimation, and tagged CO GEOS-Chem chemical transport model (CTM) as well as FLEXPART dispersion model was used in conjunction with Moderate Resolution Imaging Spectroradiometer (MODIS) Fire Hot Spot data for source attribution. HCN emission factors ranging from 0.43 ± 0.24 to 0.6 ± 0.22 g/kg and C2H6 emission factors ranging from 1.30 ± 0.49 to 2.9 ± 1.0 g/kg were observed. Trend analysis was done by fitting a trended Fourier series of various order, and a study was conducted to examine the effects of increasing the order. Higher order fits led to marginally better correlation and lower RMS in the residuals, though the confidence levels of the trends did not increase. Over-fitting issues were not observed.